ABSTRACT- Bioaccumulation of chemicals is an important fate process, essential for understanding the potential for indirect exposure of higher organisms in foodchains. As such it is frequently part of the risk assessment of chemicals in regulatory schemes. It is also increasingly being used as a trigger for further action and more recently as a "hazardous" property leading directly to emission estimates and risk management, e.g. EU-REACH. There are several tiers in addressing the potential of a chemical to bioconcentrate, transfer via higher trophic levels and indirect exposure of higher organisms. These increase in complexity and sophistication, starting with simple models, in-vitro assessments, testing in environmental organisms and environmental monitoring. There are a number of problems that arise at all levels of this assessment. These include uncertainty caused by a number of different issues; including experimental difficulties in establishing valid bioconcentration factors, conceptual difficulties in performing bioaccumulation assessments, model validity and difficulties in using monitoring data for bioaccumulation assessment purposes This poster will discuss these problems giving real examples and concentrating on chemicals that bioconcentrate and long half lifes in the environment. Using these it will be possible to demonstrate strategies for assessing indirect exposure and recommending further research to improve this assessment.